JPS63124591A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent deterioration in monitoring sensitivity, by using the same epitaxial crystal as an active layer and a photodetector for laser, and enhancing the dimensions for confining the quantum of the active layer of the laser higher than the dimensions of the quantum of the photodetector. CONSTITUTION:On an n-GaAs substrate 1, an n-Ga0.5Al0.5As clad layer 2 and non-doped GaAs/Ga0.8Al0.2As super-lattice active layer 10 are grown. A line and space pattern is formed in the direction of a resonator only at a part corresponding to the active layer 10 for laser by using an electron beam lithography method. The pattern is transferred to the super-lattice by a dry etching method, and a thin quantum line is formed. After the resist is removed, the thin quantum line of the super-lattice is embedded with Ga0.8Al0.2As, and a Ga0.5Al0.5As clad layer 4 and a p-GaAs cap 5 are grown. After electrodes 6, 8 and 9 are formed, a groove 7, which electrically isolates a laser part and a light receiving part, is formed. Thus a monolithic integrated circuit, which can monitor the oscillating intensity of the thin quantum line laser, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a monolithically integrated semiconductor laser and photoreceiver.

[Conventional technology]

Monolithically integrating a semiconductor laser with a monitor is an important theme not only for making the device more compact but also for simplifying the manufacturing process. Conventionally, such elements have been discussed at the 1983 National Conference of the Semiconductor and Materials Division of the Institute of Electronics and Communication Engineers, pp. 420-421, 83-6.

[Problem that the invention seeks to solve]

The structure of the laser and photodetector in the above conventional technology is as follows.

They have the same structure except for the element length, and only the bias voltage is applied in the opposite way. FIG. 1 is a schematic diagram thereof. GaA
This will be explained using a s/GaAtAs laser.

A p-GaAtAs cladding layer 4 sandwiching the laser active layer 10. A double heterostructure is formed by the n-GaAtAS cladding layer 2. 1 is an n-type substrate or contact layer connected to the n-side electrode 9.

Reference numeral 5 denotes a p-side contact layer, which is usually made of a p-GaAs layer, and has electrodes 6 and 8 divided into two using an element isolation groove 7. By applying a forward bias between 8 and 9 to cause laser oscillation, and applying a reverse bias between 6 and 9, p −
It becomes an i-n type photoreceiver. Since one layer 11 of the photoreceiver normally uses the same epitaxial layer as the laser active layer 1o, the process can be simplified.

V-f (i) When the double heterostructure narrow bandgap semiconductor of the active layer and photodetector is bulk QaAs,
With respect to bulk absorption 12, the oscillation wavelength of the laser is A1, and the photodetector has sufficient sensitivity.

However, if the laser active layer is a superlattice.

As shown in Figure '2, the oscillation wavelength λ of a laser using a superlattice is
2 is where the absorption 13 of the superlattice is significantly reduced, so if the superlattice 11 of the monitoring light receiver is the same as the superlattice 10 for the laser active layer, the light receiving sensitivity will be significantly reduced.

An object of the present invention is to create a superlattice in an active layer (quantum confinement in the -dimensional direction) to improve the performance of a laser.

The object of the present invention is to provide a high-performance optical integrated device that prevents a decrease in monitor sensitivity, which is a problem when making quantum wires thinner (quantum confinement in two-dimensional directions).

[Means for solving problems]

The above objective can be achieved by using the same epitaxial crystal for the laser active layer and the photodetector, simplifying the process, and increasing the quantum confinement level of the laser active layer to a level higher than that of the photodetector. Ru.

[Effect]

The quantum level in the case of one-dimensional quantum confinement is on the lower energy side compared to the two-dimensional case, so the semiconductor laser light produced in the latter case is stronger in the superlattice with -dimensional quantum confinement. be absorbed. A similar relationship holds when two-dimensional and three-dimensional confinement is performed.

The above objective can also be achieved by changing the width of the quantum wire to be confined between the laser section and the light receiver section. In this case, the narrower the width of the quantum wire, the shorter the wavelength of the optical transition.

〔Example〕

The present invention will be explained in detail below.

Example 1 n-Ga (1,5ALO, 5A
s cladding layer 2 (2 μm), undoped QaAS (1
00 people)/()a +18 At(L2A35OA superlattice active layer 10 is grown.

Using the electron beam phosphorography method, a resist pattern of 200 lines and spaces was created in the direction of the resonator only in the part corresponding to the active layer of the laser, and the pattern was transferred to the superlattice using the dry etching method. Create a thin line.

After removing the resist, superlattice quantum wires are embedded with GaαsAtα2A S, and then p-Gaα5Ato
, sAS cladding layer 4. Grow a p-GaA3 cap layer 5.

After forming the electrodes, a groove 7 is formed by dry etching to electrically separate the laser section and the photodetector section.

The active layer 10 of the laser part is a quantum wire, and the wavelength of laser oscillation is 845 nm, and the light absorption layer 11 of the photodetector is a superlattice, with a quantum level at 850 nm.

It exhibited sufficient light absorption for 845 rum laser light.

Example 2 After crystal growth to superlattice as in Example 1.

A quantum wire with a width of 100 A for the laser part and a width of 300 A for the receiver part is fabricated. The relationship between the wavelengths of the transition at this time can be expressed as
This will be explained using figures.

The figure shows the wavelength change 17 of the optical transition when a 100-layer GaAS quantum well sandwiched between barriers of ()a, BAt, and 2As is processed into a quantum wire with a width indicated by Ly. The transition wavelength when the quantum well remains as it is is indicated by 15.

16 and 14 show similar relationships when the height of the barrier is taken as flash.
Indicated by

Therefore, the transition of a 100A quantum wire is 8271m,
The transition of a 300A quantum wire is at 845nm.

The laser beam is sufficiently absorbed by the receiver.

In the embodiments of the present invention, the case of QaAs-based semiconductors has been described, but the same applies to other compound semiconductors such as InP-based semiconductors.

〔Effect of the invention〕

According to the present invention, it is possible to realize a monolithically integrated element that can monitor the oscillation intensity of an f1 wire laser with high sensitivity.

By using this method, it was possible to increase the sensitivity of the photodetector by 20 to 100 times compared to a case where the laser and photodetector have the same structure.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a device in which a laser and a photoreceiver are monolithically integrated, Fig. 2 is a diagram showing the relationship between the absorption coefficient of layer 3 and the laser oscillation wavelength, and Fig. 3 is an optical diagram of a quantum wire. FIG. 7 is a diagram showing changes depending on the width of a thin transition line. 1 is n-QaAs substrate, 2 is n-GaAtAS cladding, 3 is superlattice, 4 is p GaAtAs cladding, 5 is p
-GaAS cap layer, 6 is the electrode of the photoreceiver, 7 is the isolation groove, 8 is the laser electrode ff1. il is the light absorption area of the receiver, %10 is the laser active layer, 9 is the n-side electrode, 12
is the absorption spectrum of bulk GaAs, 13 is the absorption spectrum of the superlattice, 14.15 is the optical transition of the superlattice, 16.
17 shows the dependence of the optical transition of a quantum wire on the wire width.
, -1, Kaya 1 cause 2 figure 1 length (Vsu

Claims (1)

[Claims] 1. In an integrated optical device having at least one semiconductor laser and a light receiving element, the absorption edge of the active layer of the semiconductor laser is on a higher energy side than the absorption edge of the light absorption layer of the light receiver. A semiconductor device characterized in that dimensions of quantum confinement and/or dimensions of a quantum wire or a quantum box are selected so as to exist. 2. The above-mentioned laser active layer and the light absorption layer of the light receiver are made of the same superlattice, and only the active layer region of the semiconductor laser is made of quantum wires or quantum boxes. The semiconductor device according to item 1.